Ellipsograph



April 22, 1958 N. G. BARKER 2,831,251

ELLIPSOGRAPH Filed Dec. 2, 1955 2 Sheets-Sheet 1 Fig./

Nab/6 Barker OR BY mu am 3m April 1958 N. G. BARKER 2,831,251

ELLIPSOGRAPH Filed Dec. 2, 1955 2 Sheets-Sheet 2 Fig. 3

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Noble 6. Barker INVENTOR This invention relates generally to geometrical instruments and is more particularly concerned with an ellipsograph utilizing the pin and string method for scribing ellipses of varying dimensions.

A primary object of the invention is to provide an ellipsograph incorporating means for defining different fcal points and minor axes for the purpose of laying out ellipses of varying dimensions.

A more specific object of the invention in conformance with that set forth above is to provide an ellipsograph including an elongated major support arm incorporating a depending support element at one end, a centrally located pivot needle element depending from a central portion of the support arm, a pair of fixed focal elements on the support arm equidistant from the pivot needle element, means for simultaneously adjusting the focal elements toward and away from the pivot needle element, a minor axis support arm pivotally connected to the pivot needle element for rotation in a horizontal plane about pivot axis of the pivot pin element, a carriage assembly supported in free reciprocation on the minor axis support arm, a scribe element depending from the carriage assembly, a non-elastic, flexible force transmitting element secured to the carriage assembly and journaled around the focal elements, and resilient means on the minor axis support arm urging the carriage assembly away from the pivot needle element to the limits defined by the flexible force transmitting element.

A further object of the invention in conformance with that set forth above is to provide an ellipsograph of the character set forth which is readily and economically manufactured, easily used, and highly utilitarian, accurate and acceptable for the purpose intended.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

Figure l is a perspective view of the novel ellipsograph of the invention;

Figure 2 is a plan view of the novel ellipsograph showing in alternate positions the minor axis support arm as well as varying dimensioned ellipses which may be scribed thereby;

Figure 3 is a fragmentary sectional view taken substantially on the line 33 of Figure 1;

Figure 4 is a sectional view taken substantially on the line 44 of Figure 1;

Figure 5 is an enlarged sectional view taken substantially on the line 5-5 of Figure 1;

Figure 6 is an enlarged sectional view taken substantially on the line 6-6 of Figure 1; and

Figure 7 is a diagrammatic view of an ellipse for the purpose of defining the principle involved in the ellipsograph.

Generally speaking an ellipse is a plain curve generated by a point moving so that the sum of its distances from States Patent 0 2,831,251 Patented Apr. 22, 1958 ice two fixed points (F and F see Figure 7, called the focuses, is a constant equal to the long diameter, or major axis AB. The minor or short diameter DE is a line through the center 0 perpendicular to the major axis. The focuses maybe determined by cutting the major axis with an are having its center at oneend of the minor axis and radius equal to one-half the major axis. This instrument is especially usable when the long and short diameters, i. e., the major and minor axes are known.

The method or principle utilized in the instrument has generally been identified as the pin and string method based upon the definition of the ellipse as set forth above. Considering Figure 7, if pins are driven at the points D, F and F and a non-elastic thread or cord is tied tightly around the three pins, if the pin D is removed and a marking point or scribe is moved into the loop defined by the cord, by keeping the cord taut there will be described a true ellipse, see A Manual of Engineering Drawing by Thomas E. French, 6th edition, McGraw-Hill Book Co., 1941, pages 68 and 69.

The novel ellipsograph is indicated-generally at 10 and includes a major axis support arm 12, a minor axis support arm 14 and a carriage assembly 16.

The major axis support arm 12 comprises a tubular housing member 18 which has an elongated longitudinally extending slot 20 extending therethrough. Suitably secured on the end 22 of the tubular housing member and at right angles thereto is a depending support element as pin 24 which includes a sharpened lower end portion 26 for relatively fixed retention on a surface upon which an ellipse is to be scribed. The pin 24 includes an enlarged upper end portion 28 having a lateral recess 30, see Figure 6, into which the end 22 of the housing member extends, the pin being retained on the housing member 22 by means of a lateral set screw 32. Although a specific means has been disclosed for retaining the pin 24 on the housing member any convenient means may be incorporated to accomplish this purpose.

An elongated feed screw 34, see Figure 3, is journaled within the housing member 22 the opposite ends thereof including a reduced diameter portion 36 (only one being shown) which is journaled in a suitable bearing element 38 contained within the housing member 22 by means of a suitable set screw 40. The feed screw 34 has one reduced diameter end 36 extending out of the housing member 22 and has secured thereon a suitable knurled actuating knob 42 which is retained thereon by means of a suitable set screw 44.

Secured on the housing member 22 equidistant of the ends of the slots 20 therein is a support collar element 46, being secured thereon by means of a suitable set screw 48, for example, said collar including a bore por tion through which is journaled a pivot pin element 56, see Figure 4, said pivot pin having secured on the upper end in any suitable manner a knurled handle or knob portion 52 and being secured in the support collar 46 by means of an annular flange 54 in engagement with a recessed portion 56 of said support collar. The pivot pin element St includes a sharpened lower end portion 58 which is extendable into the surface of the material upon which the ellipse is being scribed, said sharpened lower end portion 58 being located at the portion 0 of the ellipse, see Figure 7.

A pair of focal elements 66 and 62 are located in equidistant spaced relationship from the pivot pin 50, said focal elements being comparable to the points F, and F as indicated in Figure 7. The focal elements include a carriage nut 64 which is internally threaded and disposed on the feed screw 34 the carriage nut including an outwardly extending support portion 66 being retained thereon by means of suitable screws 68, the

3 support portion having a depending portion 70, see Fig ure 5, into which is suitably secured a friction reducing roller element 72, said roller element being retained in the portion 70 by means of a suitable axle pin 74. Thus it is readily apparent that rotation of the knob 42 results in the simultaneous movement of the focal elements 60 and .62 toward or away from the pivot pin 50 for the purpose of defining a longer or shorter major axis on the ellipse.

The pin 50 incorporates at an intermediate portion thereof an enlarged support portion 78 having extending therethrough a transverse aperture'80 through which extends the end 82 of a tubular housing member 84 of the minor support arm. The tubular housing member 84 is secured in the aperture 80 by means of a suitable transverse set screw 86 extending through the portion 78 of the pivot pin.

- The tubular housing member 84 of the minor axis support arm has extending therethrough in substantially planar relationship to the pivot pin 50 longitudinal open slot 88.

The carriage assembly 16 includes a support element 90 slidably supported within the tubular housing member 84, said support element 90 having depending therefrom a scribe assembly 92. The scribe assembly incorporates a tubular portion 94 into which extends a suitable scribe element 96 which may be either a pencil lead, ink pen, etc., said scribe element 96 being retained within the tubular housing portion 94 by means of a threaded collar 98. A suitable compression spring element 100 is disposed within the tubular housing element 94 with opposite ends in engagement with the upper end Wall 102 of the portion 94, the lower end of the spring being in engagement with the scribe element 96 thus permitting upward movement of the scribe element 96 and preventing the breaking of a lead or injury to the pen. The scribe element 96 is comparable to the portion D as seen in Figure 7 and will accordingly travel with the carriage assembly within the slot 88 in a manner to be subsequently described.

The carriage assembly has extending upwardly therefrom a lug element 104 which has extending therethrough a transverse bore portion 106, said lug element including a transverse set screw element 108 which is in intersecting relationship to the bore portion 106 for engagement with a non-elastic flexible force transmitting element 110. The flexible force-transmitting element 110 comprises a loop forming element which is fixedly secured in the lug element 104 by means of the set screw element 108 and which is journaled about the focal element 60 and 62. The flexible loop forming element 110 is indicated as being a thread or cord, however, any suitable flexible non-elastic loop forming member may be utilized herein. A lug element may include a lower threaded portion 112 and be threaded into a suitable aperture in the support element 90, see Figure 4.

Rotatably supported in upward extending relationship from the support element 90 is a suitable support pin 114 upon which is journaled a storage spool element 116 on which the surplus of the flexible loop forming element 110 is stored. It will be noted that the lock screw element 108 engages an intermediate portion of the flexible element 110, the remaining portion being doubled when passing through the aperture 106 of the lug element 104 and thence around the storage spool 116.

The support element 90 has depending therefrom a tubular support element 118 which has a transverse aperture through which one end 120 of a compression spring 122 extends, the other end of the spring 122 being fixedly secured in any suitable manner with a pivot pin 50 as seen at 124. Although a specific type of spring has been disclosed it is to be understood that any type resilient means may be incorporated. to extend between the support element 90 and the minor axis support arm 14 for the purpose of urging the carriage assembly 16 away from the pivot pin 50, the purpose of the spring being for retaining the flexible loop forming element taut on the focal elements 60 and 62 in order to maintain the relationship of the scribe 96 with respect to the focal elements 60 and 62. The housing member 18 of the major axis support arm may include thereon suitable indicia of measurement 126 and 128 which will be aligned with an indicating mark on the portion 66 of the focal elements whereupon the focuses of the ellipse may be readily determined. The housing member 84 of the minor axis support arm also includes indicia of measurement 130 thereon for the purpose of determining the minor axis of the ellipse to be scribed.

Use of the instrument is believed to be readily apparent, pivot pin point 58 placed at a predetermined center, the support arm 26 is retained on a support surface in alignment with the major axis of the ellipse to be scribed, element 108 is loosened until a minor axis is defined on the minor axis support arm, the spool 116 is rotated and the flexible loop forming element 110 is tightened thereupon whereafter the set screw element 108 is secured on the intermediate portion of the flexible loop forming element 110, and upon rotation of knob 52 of the pivot pin 50 there .will be scribed an ellipse as seen in Figure 2 by means of the method previously described relative to Figure 7 of the drawings.

Various positional directional terms such as from rear, etc. are utilized here and have only a relative connotation to aid in describing the device and are not intended to require any particular orientation with respect to any external elements.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

What is claimed as new is as follows:

1. An ellipsograph comprising an elongated major axis support arm, said arm being composed of a tube, a knob at one end of said tube, a support pin at the opposite end of said tube and extending at right angles to the longitudinal axis of said tube, said tube having a downwardly opening elongated slot in the bottom part thereof, a wall at the end of said tube which has said knob, a screw coaxially arranged in said tube and having a part which passes through said wall, means fastening the part of said screw that passes through said wall to said knob so that when said knob is rotated said screw is rotated simultaneously thereby, a collar attached onto said tube intermediate the ends thereof, a pivot pin, a support connected to said pivot pin, means mounting said support on the lower part of said collar for pivotal movement of said support and said pin, a pair of focal elements mounted for movement parallel to the axis of said tube, said focal elements including members having internally threaded bores through which said screw is passed, parts of said focal elements being located in said slot in said tube, whereby said focal elements are moved in response to rotation of said knob, a minor axis support arm, said minor axis support arm having an inner extremity which is carried by said support, said minor axis support arm being hollow and having a downwardly opening and an upwardly opening slot in the walls thereof, a carriage mounted in said minor axis support arm and movable toward and away from said pivot pin, a scriber carried by said carriage, a flexible force transmitting loop, pulleys on said focal elements, a pulley constituting a part of said carriage and located above said minor axis support arm, said flexible loop being entrained over all of said pulleys, and a spring having one end reacting on said support and the other end reacting on said carriage to yieldingly bias said carriage in such direction as to main- References Cited in the file of this patent tain said loop taut during the movement of said minor UNITED STATES PATENTS axis support arm.

2. The ellipsograph of claim 1 wherein there is a lug 646329 Tmtanne "7-" 1900 connected to said carriage and passing upwardly through 5 FOREIGN PATENTS the upper slot in said support arm, said lug having a pas- 1 0 B 18 sage through which two strands of said flexible loop are 52 2 gzigi y 5 passed in order to form a guide for the flexible loop and 41 4 Germany June 1896 to retain the flexible loop engaged on the pulley of said 167089 Austria 1950 carriage, and said lug being located adjacent to said pul- 10 ley of said carriage and between it and the pulleys on said focal elements. 

